Alkyl methacrylic esters and process of making same



4 35 active chloride Fatented lid. lfid ALKYL Edward L. Kropa, East Ellis-Foster Company, .iersey tra'runoamo us'runs rnoonss or MAKING s r- Oe, N. it, assignmto a corporation of New No Drawing. Application March 31, 193?, Serial No. 134,015

v I 2 claims. (@18250-486).

This invention relates to the preparation of unsaturated esters and in particular to the dehye dration of u-hydroxy lsobutyric esters to methacrylic esters.

According to this invention. u-hydroxy isobu- 1 tyric ester is treated with a reagent capable of forming a derivative 01 the type -CH:\ I 05 0-0 3 1 R000 1 a:

'(where R. stands for an alkyl groupinspMe a metallic or non-metallic grouping ,andthevalue :n" is the valance of Me) and subjecting the 1 product to heat whereby decomposition occurs into a hydrated derivative of Me and the unsaturated ester.

As reagents capable of reacting with thenisobutyric ester may be mentioned silicon chloride, stannic chloride, phosphorus chloride and phosphorus oxychloride, sulphuryl chloride and thionyl chloride, yielding, respectively. etc onisobutyric ester, stannic omisobutyric ester, phosphoric oxybutyric ester and phosphorus oxybu gs tyric ester, sulphuric oxybutyric ester and sulphurous oxyloutyric ester. The chlorides may he very efiectively used inasmuch as they yield hydrogen chloride which escapes from the reaction f mixture.

In carrying out the invention, the hydroxy iso butyric ester is added slowly to the active ohlo ride with or without poolinglout under conditions which preclude. the-presence of moisture inas-- much as the presence of water would destroy the and decompose the resulting metallic (or non-metallic)organic derivative. 'llhe reaction mixture is then warmed under conditions which allow the escape oi hydrogen chloride.

The resulting mass is then subjeo to heat 40 treatment whereby decomposition occur into the unsaturated ester. Inasmuch as the 1 n ester is readily susceptible to polym known polymerization inhibitors such copper.

sulphur, tannic acid and the lilse'may he added 45 at this point.

The amount of the active halides used may be varied in quantity but usually it is preferable to use the halide in such a ratio as to convert all oi the halide into hydrogen halide, in other words. in stoichiometrical proportions. With phosphorus halides, one mole proportion is used to 3 mole proportions of the oxyisobutyric ester;

. with stannic and silicon des, one mole pro portion is used to 4 mole proportions oi the owgs butyric ester.

bath until hydrogen was slowly treated with 54 parts of ethyl prommateiy 0.1 part of copper hy the treatment or The ethyl methacrylate, which are"; ill- Example 1 .Phosphorus oiwchloride (16 parts) was slowly treated with parts or ethyl oxybutyrate. Hydrogen chloride gas was given ofl. The reaction mixture was warmed on a water chloride gas evolution ceased. The reaction mixture, was then distilled at atmospheric pressure and the distillate was washed with water saturated with sodium chloride, dried over anhydrous sodium sulphate and redistilled over tannic acid to yield ethyl methacrylate.

The residue remaining from the distillation was water-white, indicating that very little carbonization and polymerization had occurred. Phosphorus trichloride under similar conditions behaves in an analogous manner.

Example la -Silicon tetrachloride (17 parts) carbutyrate and the reaction miature warmed until hydrogen chloride gas ceased to he evolved. Ap-

bronze powder was added and the mixture heated in an oil bath, the temperature '01 which was about 200 C. The dis-= tillate was washed with brine, dried over sodium sulphate and redlstilled to yield ethyl metha crylate. Stannic chloride under 1.:-...- conditions yields the unsaturated acrylic ester.

It is readily apparent from this invention t a large number oi active chlorides will react with the oxyisobutyric esters resulting in the torma= tion or a neutral organic -inorganie ester. The organic-inorganic ester on thermal decomposition decomposes into the mecrylic ester end the inorganic residue.

- The methacrylic esters may he poeriaedto high-molecular weight derivatives of a resinous naturecby means of ondizinlg agents and the hire.

in'theabove examples the process is illustrated ethyl oxyisoloutyrate to give ethyl methacrylate. Esters oi! other alcohols give a methacrylic ester corresponding to the alcohol. For example, methyl oxyisohutyrate yields methyl methacrylate. hiirrtures or esters may also he treated.

The reaction of phosphorus chloride with oxyisohutyrates has been described in the literature: However, a large excess of phosphorus chloride was used and the product was polerized to a great extent. In the present invention, substantially stoichiometrical proportions of resntants are used with the advantages not only on the score of economy but also from the standpoint crease of pulation and purity .of the resulting product.

trated in tneiorego, has a somewhat 'w dill boiling point than methyl methacrylate. when the monomeric'esters are polymerized, however, the melting. points of the polymeric derivatives are reversed, that is, the polymethyl methacrylate has a higher softening point'than the polyethyl methacrylate; This is advantageous when injection molding is employed because theethyl methacrylate permits a 10 r temperature in the injection molding apparatus. However, by making mixtures of methyl and ethyl methacrylate the temperature used in' injection molding can be suitably adjusted, and for this purpose I recommend a proportion ranging from 1 part 01' methyl methacrylate to 3 parts of ethyl methacrylate up to, say, the reverse proportion, namely, 3 parts of the methyl to 1 part of the ethyl compound, but I do not limit myself to such range of mixtures as modifications thereof can bemade to suit the particular require-' ment of injection molding or other molding operation.

Also, it is possible to polymerize the ethyl methacrylate with methacrylic acid or other active unsaturated acids to increase the softening point of the resulting polymeric material. Similarly, methacrylic acid may be polymerized with methyl methacrylate toyield a material of higher softenamaze? ing point than the polymethyl methacrylate. A

derivative of this type with a higher softening point, although it requires higher temperature in an injection molding apparatus, is of advantage in yielding a product less susceptible to cold flow.

It may be noted, however, that in cop'olym'erization the ethyl methacrylateappears to be particularly advantageous because of the lessened liability of formation of gas bubbles at the temperatures used in polymerizing when such polymers are being form What I claim is:

1. The process for the preparation of an alkyl ester oi methacrylicacid which comprises reacting a silicon halide with substantially stoichiometrical proportions of an'alkyl ester of a-hydroxy isobutyric acid to form analkyl oxyisobutyrate silicate and heating said product, whereby decomposition into a hydrated derivative of silicon and the unsaturated ester occurs.

, 2. The process of making methyl methacrylate which comprises reacting methyl hydroxyisobutyrate with silicon tetrachloride to form a methyl oxyisobutyrate silicate and heating said product, whereby decompositioninto a hydrated derivative of silicon and the unsaturated ester occurs. f

@WARD L. KROPA. 

